The present invention relates generally to illumination devices for incorporation into wristwatches. More specifically, this invention relates to a multifunction illumination assembly for incorporation into wristwatches whereby LED lighting elements are provided for use to illuminate the watch face, to act as a watch locator and to serve as a flashlight.
In the prior art, various types of illumination devices have been proposed for wristwatches to enable reading the time under poor light conditions. Primarily, phosphorescent materials have been employed on watch dials with varying degrees of success and all suffering from the well-known shortcoming of being difficult to see particularly with the passage of time as the phosphorescence decreases. Moreover, the phosphorescent material requires recharging by being exposed to light in order for the phosphorescence to be maintained. In addition, the luminous materials used in dials of the foregoing watches also lose their light emitting capacity with age and have generally provided substantially less than fully satisfactory performance.
As an alternative to the use of phosphors, electric devices for watch illumination have been employed with some limited success. Such devices usually take the form of small incandescent bulbs powered by a battery and arranged inside the case of the wristwatch, assisted by light pipes or reflectors to enable the numerals on the dial to be seen. In other assemblies, it has been proposed to carry a small battery outside the watchcase in a special attachment connected to the watchband. In this case, an incandescent bulb is carried in the watch crystal, connected to the battery by lead-in wires, and operated by a switch. Further, the prior art discloses an incandescent bulb carried on the watchcase and connected to a battery in an attachment connected between the watchband and the case by means of lead wires. A deformable or flexible wall allows the circuit to be closed to illuminate the dial by pressing the flexible wall.
In all of the foregoing arrangements, the lead wires passing between the power source in the watchband attachment and the incandescent bulb in the case or crystal are subject to possible malfunction, due to breakage caused by the constant and repetitive movement between the case and the attachment. Also, the arrangements described are not easily utilized as a flashlight if such functionality is desired by the user.
Another shortcoming of many of the prior art devices is that they inefficiently rely upon a relatively powerful illumination source, which attempts to illuminate the entire area of the dial by simple radiation from the source. Often the result causes portions of the dial nearest the light source to become overly illuminated in order that the portions spaced from the light source may have adequate illumination. Additionally, this approach tends to cause shadows especially with curved surfaces and three-dimensional objects. Other drawbacks of the prior known devices for providing dial illumination include the fact that they are bulky and are frequently both delicate and expensive. In general, these devices employing incandescent filament operated bulbs have not been accepted for portable devices due to the fact that they require substantial battery capacity for their operation due to their substantial power requirement.